1. Field of the Invention
The invention relates to a radar viewing apparatus comprising a cathode ray tube including an afterglowing viewing screen, a deflection unit associated with the tube and an electronic constructional group for controlling the cathode ray tube electrodes and the deflection unit with at least the cathode ray tube and the deflection unit arranged in a common housing.
2. Description of the Prior Art
The cathode ray tube used for the representation of the picture in an important structural element for a radar system. It is on this tube that the user is to recognize as clearly as possible the radar targets and perhaps the measuring rings, thus enabling him to evaluate them as unambiguously and as safely as possible. The radar screens are mostly green or orange colour. Green radar screens are preferred aboard a ship while the orange-coloured radar screens are for a considerable part used in flight security or air traffic control services for example. In connection with flight security services the environmental brightness at the radar viewing screen does not change since a darkened room is used. On the bridge of a ship, however, the environmental brightness changes considerably with the transition from day to night. As the maximum of the sensitivity characteristic of the eye is at 555 NM (nonometer, i.e. 10.sup.-9 meters or millimicrons) the green radar screen has frequently been preferred up to now for the radar systems of ships. Particularly during dusk and dawn, however, the visual perception or sensitivity grows considerably less, but also with sudden transistions from bright to dark the visual perception or sensitivity is reduced. As in the case of night traffic the environmental brightness is missing, the green radar very much dazzles the viewer because in that case particularly strong transitions from bright to dark will occur when the viewer during a journey at night averts his look from the radar viewing apparatus and looks into the darkness. An optimum sensitivity is no longer given.